The invention relates to an apparatus for preparing curd and feeding same to a curd processing apparatus, comprising a number of curd tanks and a pipe system connected with the curd tanks and provided with pumping means to feed curd from the curd tanks to the curd processing apparatus.
Such an apparatus is known from practice. The known apparatus comprises a number of curd tanks, also referred to as curd vats, cheese vats or cheese tanks, in which, in a known manner, through addition of starter and rennet to milk, a whey/curd mixture is prepared. By stirring and cutting with cutting frames present in the curd tanks, whey is released from the curd. The whey can at least partly be removed from the curd tank. The remaining whey/curd mixture is supplied to a curd processing apparatus via suitable piping and with suitable pumping means. Such curd tanks are for instance commercially available under the name of Tetra Tebel OST tank. An example of a curd processing apparatus is the cheddar machine available under the name of Tetra Tebel Alfomatic, which can be used, for instance, for producing cheese of the Cheddar type or the Pasta Filata type.
Known from practice is an apparatus which comprises a relatively large number of curd tanks, for instance 10 to 14 curd tanks, which are arranged in two rows opposite each other. Each curd tank has a curd discharge pipe, provided with a curd valve, which terminates in a ring line extending along all curd tanks, which ring line is coupled at one end, via two curd pumps, with an inlet section of a curd processing apparatus.
A problem of the known apparatus is that the curd vats in fact function batchwise, whereas other machines that are used in the cheese production process, such as the pasteurizer mostly used prior to the curd tanks, and the curd processing apparatuses following curd preparation, such as, for instance, a cheddar machine, a salt feeder, a block former and the like, perform a continuous process. This difference in functioning does not promote the uniformity and consistency of the curd treatment necessary to obtain an end product of high quality.
In practice, the pump-out (draining) time for a curd tank can vary considerably. Thus, for instance, pump-out times of the order of 15 to 20 minutes occur, but also pump-out times of the order of 50 minutes. This has consequences for the acidity and the moisture content of the curd. Curd particles that are pumped out of a vat last are smaller and have a higher acidity than the curd particles that are pumped out of a curd vat at the beginning of a pumping cycle. Also, the curd particles at the end of a pumping cycle have a lower moisture content than the curd particles pumped out of a curd vat at the beginning of a pumping cycle. The moisture content in turn has an influence on the effect of the operation of the salt feeder, which is to feed dry salt to the curd in the curd processing apparatus. Since the salt stops bacteriological activity, the salt supply is very important for the maturing process of the cheese produced. The composition of the eventual product depends on the composition of the curd at the time when the salt is being added and also on the accuracy of salt metering. Accordingly, it is important that the pump-out time of a curd vat be kept as short as possible in order to obtain a curd quality as constant as possible. Furthermore of interest is that through a shortening of the pump-out time, also a larger processing capacity of the apparatus is obtained. It is also important that the curd be fed uniformly to the curd processing apparatus.
A shortening of the pump-out time of a curd vat and a uniform curd supply to a curd processing apparatus can be effected by increasing the pumping capacity. However, there are limitations to this in that the speed of movement of the curd in the pipe system must remain below a particular limit to prevent damage to the curd structure. The speed of movement of the curd in a particular plant can be lowered by choosing the diameter of the piping to be larger. However, this has various inherent drawbacks. First of all, valves for pipes of a large diameter, for instance 6 inches, are difficult to obtain in many parts of the world. Also, such valves are very costly and not quickly operable.
In addition, to clean piping, a particular minimum flow velocity of the cleaning liquid is required. Accordingly, with pipes having a large diameter, actually an extra high pumping capacity is required for the cleaning liquid. The required flow of the cleaning liquid with 6-inch pipes, for instance, is more than twice as high as with 4-inch pipes.